Throttle valve arrangement for noise control in compressor-expander

ABSTRACT

A compressor-expander for use in air conditioning having a compressor side and an expansion side housing a vane-type rotor of the positive displacement type, each side having inlet and outlet ports and connected with an associated heat exchanger so that a charge of air drawn into the compressor side is compressed between adjacent vanes, cooled to remove heat of compression, and then expanded between adjacent vanes for discharge in the cold state. The compressor inlet port and expander outlet port are so positioned that the volume of an exiting charge of air is less than the volume of an entering charge of air in predetermined ratio so that air is discharged at nominally ambient pressure. An adjustable throttle valve is provided at one of the ports, preferably the expander inlet or outlet port, so that the initial pressure of the exiting charge is more nearly equal to the pressure on the discharge side of the expander outlet port, thereby to minimize explosive puffing of air and its attendant noise upon traverse of the vanes past the expander outlet port, the throttle valve being adjusted for minimum noise under a given set of operating conditions. In one of the aspects of the invention, means are provided for sampling the initial discharge pressure of an exiting charge of air and for comparing the pressure with that on the discharge side of the expander outlet port, the pressure differential being utilized for automatic and constant correction of the throttle valve to the minimum noise condition.

United States Patent [191 NOISE CONTROL IN COMPRESSOR-EXPANDER [75] Inventor: Thomas C. Edwards, Casselberry,

Fla.

[73] Assignee: The Rovac Corporation, Maitland,

Fla.

[22] Filed: Apr. 23, 1974 [21] Appl. No.: 463,296

[52] US. Cl. 62/296; 181/46; 62/402; 415/181 [51] Int. Cl. F25d 19/00 [58] Field of Search 181/46, 36, 56, 71; 62/402,1296, 172; 415/181 [56] References Cited I UNITED STATES PATENTS 2,075,316 3/1937 Tyden 181/46 2,585,570 2/1952 Messinger.... 62/402 2,691,274 10/1954 Whitney 62/172 2,871,672 2/1959 Boydell.... 62/172 3,083,546 4/1963 Tierek 62/172 3,120,109 2/1964 Weil 62/402 3,686,893 8/1972 Edwards 62/402 [111 3,884,664 Edwards May 20, 1975 THROTTLE VALVE ARRANGEMENT FOR [57] ABSTRACT A compressor-expander for use in air conditioning having a compressor side and an expansion side housing a vane-type rotor of the positive displacement type, each side having inletand outlet ports and connected with an associated heat exchanger so that a charge of air drawn into the compressor side is compressed between adjacent vanes, cooled to remove heat of compression, and then expanded between adjacent vanes for discharge in the cold state. The compressor inlet port and expander outlet port are so positioned that the volume of an exiting charge of air is less than the volume of an entering charge of air in predetermined ratio so that air is discharged at nominally ambient pressure. An adjustable throttle valve is provided at one of the ports, preferably the expander inlet or outlet port, so that the initial pressure of the exiting charge is more nearly equal to the pressure on the discharge side of the expander outlet port, thereby to minimize explosive puffing of air and its attendant noise upon traverse of the vanes past the expander 4 outlet port, the throttle valve being adjusted for minithe minimum noise condition.

8 Claims, 5 Drawing Figures Pmwmmz m $884,664

OOOOOOOO OOOOOOOOOOO OOOOOOOOOOO THROTTLE VALVE ARRANGEMENT FOR NOISE CONTROL IN COMPRESSOR-EXPANDER In a single fluid air conditioning system using a comthe exhaust pressure differs slightly from ambient pressure, creates an inherent noise problem. Even where a system is carefully designed, by reason of proper port placement and the like, to exhaust at ambient pressure, the design conditions including ambient pressure, temperature and humidity, as well as variations in leakage and driving speed, are unfortunately subject to constant change, resulting in a pressure differential, and hence noise.

It is, accordingly, an object of the present invention to provide simple and effective means for minimizing noise produced in a single fluid, compressor-expander type of refrigeration unit. It is a related object to provide noise reducing means which is easily adjusted for prompt compensation for any and all changes in ambient conditions or other conditions affecting the operation of the device.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings, in which:

FIG. 1 is a diagrammatic cross section of a refrigeration unit of the compressor-expander type with associated heat exchanger and utilizing one or more throttle valves in accordance with the present invention.

FIG. 2a is a diagram showing the entering charge of air defined by adjacent vanes.

FIG. 2b is a similar diagram showing an exiting charge of air defined by adjacent vanes.

FIG. 3 is a sectional view showing means for minimizing noise constantly and automatically in accordance with changes in operating conditions.

FIG. 4 is a fragmentary view taken along line 4-4 in FIG. 3.

While the invention has been described in connection with certain preferred embodiments, it will be understood that I do not intend to be limited by the particular embodiments shown, but I intend, on the contrary, to cover the various alternative and equivalent forms of the invention included within the spirit and scope of the appended claims.

Turning now to FIG. 1, there is shown an air conditioning unit of the compressor-expander type having a frame or stator 11 in which is mounted a rotor 12 on a shaft 13, the ends of the shaft being journaled in suitable end members (not shown). The shaft is rotated, in the direction of the arrow, by suitable driving means 14. Slidably mounted in the rotor are vanes 21-30 inelusive.

As shown, the left-hand side, referredto as the compressor side" has an inlet port 31 and an outlet port 32. The right-hand or expansion side has an inlet port 33 and an outlet port 34. Ducts or conduits 35, 36 provide communication to the respective ports 31, 34.

All of the vanes are pressed outwardly into effective engagement with the interior wall 37 of the frame 11 by means of a spring band 38. Adjacent vanes thus define enclosed-compartments between them, providing positive displacement of air which is progressively compressed on the left-hand side and expanded on the right-hand side.

For removing the heat of compression, a heat exchanger 40 is used having an inlet 41, an outlet 42, and plurality of heat exchanging fins 43. For further details, reference may be made to my prior US. Pat. No. 3,686,893 which issued on Aug. 29, 1972 and my application Ser. No. 400,965 filed Sept. 26, 1973. The profile of the inner wall 37 of the frame is preferably of oval configuration. Thus as the rotor rotates in the direction shown, the compartment indicated at 51 and defined by vanes 21, 22 increases in volume, with air being drawn in through the inlet port 31 until vane 21 reaches the end 52 of the inlet port, at which time the compartment ,has an entering charge of air at substantially atmospheric pressure. The volume of such entering charge is proportional to the projected area of the compartment which has been indicated by crosshatching A in FIG. 2a.

The air in the compartment 51 is progressively compressed and squeezed, at high pressure, through the compressor outlet port 32 into the heat exchanger 40, where the heat of compression is given off. The air passes through the heat exchanger at substantially constant pressure, flowing, while still at a high pressure,

7 into the expander inlet port 33. As the rotor continues its rotation, taking the compartment 53 between vanes 27, 28 as typical, the vane 28 will reach the threshold 54 of outlet port 34, which is the condition illustrated in FIG. 2b. The exiting charge of air in compartment 53 has a volume which is indicated by the crosshatched area B. As a matter of design, the end 52 of the inlet port and the threshold 54 of the outlet port are so positioned that the volume of a cold dense exiting charge of air is less than the volume of an entering charge of air in such ratio (area B to area A) that the masses of air are the same in both of the compartments 51, 53. Under such circumstances, the air will be discharged at -.substantially the same pressure as it was taken in, that is, at ambient pressure.

While discharge of the air at ambient pressure has been recognized as desirable it is not possible to design in this condition with precision, particularly in the face of a change in operating conditions. For example, where conditions are such that an exiting charge of air in the compartment. 53, as it is about to be discharged (FIG. 2b), is at a pressure whichis higher than ambient, that is, higher than that which exists at the discharge side of the outlet port 34, an explosive outward puff. will occur as the vane 28 clears the threshold 54 of the outlet port. A similar explosive puff will occur upon passage of the next vane 27, and this is repeated for each vane at a cyclic rate which is ten times greater than the speed of rotation of the shaft (there being ten vanes). The result is noise in the form of a sonic vibration having a pitch which depends upon the driving speed and which has an amplitude which depends upon the pressure differential. Indeed, production of noise is rather efficient since the mechanism of its production,

chopping of air at a discharge port, is similar to that of the discharge side of the outlet port to be precisely the same as the pressure of the exiting charge of air. For example, in accordance with the invention a throttle tion with the outlet port 34, with the throttling action producing a back pressure slightly increasing the pressure in the conduit to the point where it is more nearly the same as the initial pressure of the exiting charge. Thus, I provide in the conduit 36, abutterfly valve 60 having a shaft 61 and adjusting arm 62. The butterfly valve is preferably located a short distance downstream from the outlet port 34 to define a small pressure equalizing chamber 63. With the throttle valve 60 in its minimum noise position, and thus with the pressure in the adjacent chamber 63 more nearly the same as the initial pressure of the exiting charge of air 53, there will be no sudden or explosive puff when the vane 28 reaches the threshold 54. Instead, at the instant of opening of the compartment 53 no air movement will take place except that which results from reduction of compartment size during the course of counterclockwise movement. Thus, air is relatively gradually squeezed out of the compartment 53 into the chamber 63 with minimum noise. While there will be cyclical variations of pressure within the chamber 63, such variations will tend to be of low amplitude because of simultaneous discharge of adjacent chambers in different phases of their discharge cycle.

In carrying out the present invention I have found that it is possible to achieve the same desirable result by use of a throttling valve, at alternative points in the system, for example, in the inlet conduit 35. Here a butterfly valve, indicated at 70, having a shaft 71 and adjusting arm 72, is mounted in inlet conduit 35. The effect of varying the throttle valve 70 is to cause the air which flows to the compressor inlet opening 31 to be varied with respect to ambient pressure, so that the mass of air which is admitted to the compartment 51 differs from that which would otherwise be admitted. Since the mass of air per compartment is changed on the compression side, it. will be correspondingly changed on the expansion side, resulting in a change in the'initial pressure of a typical exiting charge of air 53, thereby avoiding any explosive puff of air as the vane 28 clears the edge 54 of the outlet port.

I have also found that effective control of initial outlet pressure may be achieved by a throttle valve mounted in the heat exchanger loop, for example, adjacent the expansion side inlet port 33 as indicated at 80 and with a shaft 81 and adjusting arm 82. The throttle valve 80 has the effect of controlling the pressure which exists in the heat exchanger, thereby to compensate for any change in ambient condition. For example, if the ambient pressure existing at the outlet port increases, the throttle valve 80 is adjusted to decrease the pressure drop in the heat exchanger, and vice versa. The throttle valve 80, it may be noted,-is also effective to compensate for a variation in inlet humidity. Thus if an increase in inlet humidity is experienced, the temperature and pressure on the expansion side tend toincrease due to increased condensation causing the initial pressure of the exiting air to exceed ambient pressure. To bring the pressure of the exiting air back down to the ambient level, the throttle valve 80 is adjusted to a more restrictive condition.

Nor is it necessary for the throttle valve in the heat exchanger loop to be located immediately adjacent the such as the throttle valve 90 having a shaft 91 and adjusting arm 92.

In carrying out the present invention the existence of a throttle valve in one of the illustrated positions is taken into account in the initial design of the compressor-expander. That is tosay, in arriving at a design of compressor-expander it is assumed both that the throttle valve is in place and that it is adjusted to midposition to give a certain normal amount of throttling valve at such'mid-position, and, under assumed ambient conditions, discharge will take place at ambient pressure with minimum noise. Upon a change of condition in either direction it is then possible to minimize noise by moving the throttle valve in either direction from the mid-position as appropriate.- While a single throttle valve is capable of accommodating a rather wide range of conditions, it will be understood that the invention is not limited to use of a single throttle valve and that the range of accommodation may be increased by using two or more throttle valves in the positions shown, either with individual or ganged adjustment.

Also while it is convenient to use a throttle valve of the butterfly type for reasons of economy and because of its balanced design, requiring minimum operating torque, it will be apparent to one skilled in the art that any other type of valve may be used which is capable of providing the throttling action.

In accordance with one of the aspects of the invention means are provided for automatically and continuously adjusting a throttling valve to minimize noise brought about by changes in operating conditions.

Such an arrangement is disclosed in FIGS. 3 and 4 where similar reference numerals, with addition of subcomparing the pressure of the exiting charge with the expansion side inlet port. It may, as shown at the lefthand side of FIG. 1, occupy a more upstream position pressure existing on the discharge side of the outlet port 34a and for bringing about a corrective change in valve setting as a result of any differential which may be detected. Tosample thepressure in the exiting charge of air 53a, a sampling port is provided spaced a short distance ahead of the outlet port 34a. Such sampling port is connected via a small conduit 101 and auxiliary throttling, or needle, valve 102 to a differential detector 103 having a diaphragm 104 and plunger 105. The opposite, or right-hand, side of the diaphragm is connected by a conduit 106 to the'chamber 63a which forms the-initial portion of the discharge conduit 36a. The plunger may be conveniently connected as by a pin 107 to the end of the arm 62a of the throttle valve. 7

Thus as long as the pressure of the exiting charge of air is the same as the pressure which exists on the discharge side of the outlet port 34a, the condition for minimum noise is satisfied and there will be no tendency for the diaphragm to move, so that the throttle valve 60a will remain in its existing position. However, in the event that the operating conditions change so that the temperature of an exiting charge of air increases above the equilibrium level, accompanied by through the sampling port, causes the diaphragm to move to the right thereby rocking the throttling valve slightly toward the closed position resulting in an increase in back pressure in the chamber 63a. This slightly increases the pressure on the right-hand side of the diaphragm, conducted thereto via the conduit 106, so that the diaphragm achieves a new equilibrium position of equalized pressure corresponding to the condition of minimum noise. The auxiliary throttle, or needle, valve 102 is adjusted to provide the optimum amount of damping thereby to make the control arrangement less susceptible to rapid pressure fluctuations of a casual nature.

While it is preferred to compare the pressure of the exiting charge of air, as sampled by the auxiliary port 100, to the pressure which exists on the discharge side of the outlet port 34a (via conduit 106), it is not essential that the conduit 106 be returned to the chamber 63a, and such conduit 106 may, instead, be opened up directlyto the ambient atmosphere as indicated at 110.

Also while use may be made of the throttle valve 60a to produce variations in back pressure in the expansion side discharge conduit 360, the invention is not limited thereto and the output plunger 105 of the differential sensor, may, instead, be connected to the throttle valve 70 by a suitable mechanical link, not shown, but which heat exchanger, the throttle valve being adjustable for alternatively enlarging and narrowing the cross section of the air stream to vary the pressure drop in the heat exchanger so that the initial pressure of an exiting ing a compressor-expander including a frame defining a chamber having a compression side and an expansion side, a vane type rotor means mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove the heat of compression, expanded between adjacent vanes, and discharged in the cold state, a conduit connected to the expansion side outlet port, a throttle valve in the conduit for alternatively enlarging v and narrowing the cross section of the air stream so is indicated diagrammaticallyat 111. In similar fashion I the output of the differential detector may be connected, if desired, to the throttle valves in positions 80, 90.

It will be seen that the construction described above amply fulfills the objects of the invention. One skilled ,in the art will appreciate that it is a difficult matter to tailor a compressor-expander unit precisely to a given set of conditions so as to avoid pressure pulses, either positive or negative, at the expansion side outlet port, particularly in the face of variable changes in operating conditions. In practicing the present invention, a throttle valve may be incorporated in the construction at minor expense with'a convenient linked control to provide a touch-up pressure adjustment, either manually asset forth in FIG. 1 or by simple automatic means as described in connection with FIG. 3 to compensate, not only for a change in'ambient condition, but a change in any other operating condition including leakage or speed.

The term vanes as used herein will be understood to broadly include any partition means defining chambers which are progressively compressed in size, and enlarged, for the compressor and expander functions.

What I claim is:

1. In a refrigeration system the combination comprising a compressor-expander including a frame defining a chamber having a compression side and an expansion side, a vane type rotor means mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the' compression side outlet port and the expansion side inlet port so that upon driving of the rotor means air drawn into the compression side is compressed be-v that the air pressure in the conduit is more nearly equal to the initial pressure of an exiting charge of air thereby to minimize explosive puffing of air and its attendant noise upon traverse of the vanes past the expansion side outlet port.

3. In a refrigeration system the combination comprising a compressor-expander including a frame defining a chamber having -a compression side and an expansion side, a vane type rotor means rotatably mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means a stream of air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove heat of compression, expanded between adjacent vanes and discharged in the cold state, and an adjustable throttle valve at at least one of the ports for alternatively enlarging and narrowpuffing of air and its attendant noise upon traverse of the vanes past the expansion side outlet port.

4. In a refrigerationsystem the combination comprising a compressor-expander including a frame defining a chamber having a compression side and expansion side, a vane type rotor means rotatably mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means a stream of air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove heat of compression, and expanded between adjacent vanes for discharge of the stream in the cold state, and an adjustable throttle valve means positioned in the air stream for alternatively enlarging and narrowing the cross section of the air. stream so that the initial pressure of an exiting charge of air is more nearly equal to the ambient pressure into which the charge exits, thereby to minimize explosive puffing of air and its attendant noise upon passage of the vanes at the expander outlet port, the throttle valve means being located in at least one of the ports not including the compression side outlet port.

5. In a refrigeration system, the combination comprising a compressor-expander including a frame defining a chamber having a compression side and an expansion side, a vane,type rotor means rotatably mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means a stream of air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove heat of compression, expanded between the adjacent vanes and discharged in the cold state, means defining a discharge conduit connected to the expansion side outlet port, an adjustable throttle valve at one of the ports for alternatively enlarging and narrowing the cross section of the air stream, means for sampling the initial pressure of successively exiting charges of air, means for sampling the pressure in the conduit, and means responsive to the differential between the two sampled pressures for correctively adjusting the throttle valve to make the sampled pressures more nearly equal thereby to minimize explosive puffing of air and its attendant noise in the conduit at the expansion side outlet port.

6. The combination as claimed in claim 5 in which the sampling means includes an auxiliary port lying just ahead of the expansion side outlet port.

7. The combination as claimed in claim 6 in which the differential responsive means is in the form of a diaphragm interposed between the auxiliary port and the discharage conduit, the diaphragm being coupled to the throttle valve.

8. The combination as claimed in claim 7 in which the diaphragm is provided with damping means to eliminate fluttering thereof. 

1. In a refrigeration system the combination comprising a compressor-expander including a frame defining a chamber having a compression side and an expansion side, a vane type rotor means mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove the heat of compression, expanded between adjacent vanes, and discharged in the cold state, and a throttle valve in the path of the air flowing through the heat exchanger, the throttle valve being adjustable for alternatively enlarging and narrowing the cross section of the air stream to vary the pressure drop in the heat exchanger so that the initial pressure of an exiting charge of air more nearly matches the pressure of the air at the discharge side of the expansion side outlet port, thereby to minimize explosive pufFing of air and its attendant noise upon traverse of the vanes past the expansion side outlet port.
 2. In a refrigeration system the combination comprising a compressor-expander including a frame defining a chamber having a compression side and an expansion side, a vane type rotor means mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove the heat of compression, expanded between adjacent vanes, and discharged in the cold state, a conduit connected to the expansion side outlet port, a throttle valve in the conduit for alternatively enlarging and narrowing the cross section of the air stream so that the air pressure in the conduit is more nearly equal to the initial pressure of an exiting charge of air thereby to minimize explosive puffing of air and its attendant noise upon traverse of the vanes past the expansion side outlet port.
 3. In a refrigeration system the combination comprising a compressor-expander including a frame defining a chamber having a compression side and an expansion side, a vane type rotor means rotatably mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means a stream of air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove heat of compression, expanded between adjacent vanes and discharged in the cold state, and an adjustable throttle valve at at least one of the ports for alternatively enlarging and narrowing the cross section of the air stream to make the initial pressure of an exiting charge of air more nearly equal to the ambient pressure just outside the expansion side outlet port, thereby to minimize explosive puffing of air and its attendant noise upon traverse of the vanes past the expansion side outlet port.
 4. In a refrigeration system the combination comprising a compressor-expander including a frame defining a chamber having a compression side and expansion side, a vane type rotor means rotatably mounted in the chamber for positive displacement of air in the form of entering and exiting charges, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means a stream of air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove heat of compression, and expanded between adjacent vanes for discharge of the stream in the cold state, and an adjustable throttle valve means positioned in the air stream for alternatively enlarging and narrowing the cross section of the air stream so that the initial pressure of an exiting charge of air is more nearly equal to the ambient pressure into which the charge exits, thereby to minimize explosive puffing of air and its attendant noise upon passage of the vanes at the expander outlet port, the throttle valve means being located in at least one of the ports not including the compression side outlet port.
 5. In a refrigeration system, the combination comprising a compressor-expander including a frame defining a chamber having a compression side and an expansion side, a vane type rotor means rotatably mounted in the chamber for positive displacement of air in the form of entering and exiting charGes, the frame defining compression side inlet and outlet ports as well as expansion side inlet and outlet ports, a heat exchanger connected between the compression side outlet port and the expansion side inlet port so that upon driving of the rotor means a stream of air drawn into the compression side is compressed between adjacent vanes, cooled in the heat exchanger to remove heat of compression, expanded between the adjacent vanes and discharged in the cold state, means defining a discharge conduit connected to the expansion side outlet port, an adjustable throttle valve at one of the ports for alternatively enlarging and narrowing the cross section of the air stream, means for sampling the initial pressure of successively exiting charges of air, means for sampling the pressure in the conduit, and means responsive to the differential between the two sampled pressures for correctively adjusting the throttle valve to make the sampled pressures more nearly equal thereby to minimize explosive puffing of air and its attendant noise in the conduit at the expansion side outlet port.
 6. The combination as claimed in claim 5 in which the sampling means includes an auxiliary port lying just ahead of the expansion side outlet port.
 7. The combination as claimed in claim 6 in which the differential responsive means is in the form of a diaphragm interposed between the auxiliary port and the discharage conduit, the diaphragm being coupled to the throttle valve.
 8. The combination as claimed in claim 7 in which the diaphragm is provided with damping means to eliminate fluttering thereof. 